The preexisting technology will be discussed in reference to FIG. 3. As shown in FIG. 3, an engraving head 50 comprises a body housing that includes an end portion 52 and a top portion 53 that are joined together. Cap 51 attaches to the upper portion of end portion 52. The body housing 54 mounts to an engraving apparatus (which is not shown) and moves in X and Y directions by a movement means attached to the engraving apparatus (which is not shown). In addition the prior art contains an up-and-down movement means (which is not shown) that moves body housing 54 upward and downward. The up-and-down movement means may be an air cylinder, a sliding mechanism or the like. The up-and-down movement means couples to the engraving head 50.
The body housing 54 includes a vibration generating mechanism used in conjunction with compressed gas to cause engraving stylus 60 to vibrate slightly up and down. The vibration generation mechanism will be discussed below. A compressed gas supply port 51a is provided on cap 51. The compressed gas supply port 51a continuously supplies the compressed gas to inner room 55 of the end portion 52. The compressed gas enters inner room 55 and flows downward through penetrating holes 55a and encounters O-ring 56. The introduction of the compressed gas increases the gas pressure within inner room 55. (As the volume of the compressed gas increases within inner room 55, the pressure of the gas increases.)
When the gas pressure applied to O-ring 56 is less than a predetermined value, O-ring 56 is energized upward. The coils of helical compression spring 57 extend upward generating an upward movement of flanged portion 60a and O-ring 56. O-ring 56 is energized upward to cover penetrating holes 55a, which are formed at the lower end of end portion 52. As the gas flows into inner room 55, the pressure increases and energizes O-ring 56 downward.
When the gas pressure applied to O-ring 56 exceeds a predetermined value, engraving stylus 60, O-ring 56 and flanged portion 60a are energized downward against the energizing force of helical compression spring 57. This downward motion of O-ring 56 creates small spaces between O-ring 56 and O-ring containing groove 52a. These small spaces permit the compressed to pass into the engraving stylus operating room 53a of top portion 53. After entering engraving stylus operating room 53a, the compressed gas flows through a pair of discharge holes 53b and exits top portion 52.
As the compressed gas exits, the pressure decreases within engraving head 50, and the gas pressure applied to O-ring 56 falls below the predetermined value. Once again, O-ring 56 and engraving stylus 60 are energized upward. Due to the decreased pressure, helical compression spring 57 expands upward generating an upward movement of flanged portion and O-ring 56. O-ring 56 is energized upward to cover penetrating holes 55a. As previously discussed, the gas pressure inside inner room 55 increases again.
The introduction of the compressed gas generates the intermittent expansion and contraction motion of the helical compression spring, which in turn causes O-ring 56 and engraving stylus 60 to slightly vibrate up and down.
During the vibration of engraving stylus 60, the up-and-down movement means (which is not shown) guides and lowers the entire engraving head 50 to press the tip of engraving stylus 60 against an engraving surface T'. The up-and-down movement means may be an air cylinder, a sliding mechanism or the like. Then, the engraving head 50 is moved in the X and Y directions by the movement means to engrave letters, symbols, figures or the like on the engraving surface T'.
In order to produce engravings that are not expressed with a single brush stroke on an engraving surface, the engraving apparatus of the prior art must stop engraving, the up-and-down movement means lifts the entire engraving head 50 and the movement means repositions according to the desired X and Y coordinates. Next, engraving head 50 is moved downward at a predetermined position and the engraving procedure is resumed.
In order to press the tip of engraving stylus 60 against engraving surface T' during engraving and to perform engravings that are not expressed with a single brush stroke on the engraving surface, the prior art requires that the engraving apparatus includes an up-and-down movement means. The addition of the up-and-down movement means increases the cost and the size of the engraving apparatus. Furthermore, the repetitive operations needed to perform engravings that are not expressed with a single brush stroke on the engraving surface is time consuming. As discussed above, the prior art requires that the engraving apparatus pauses the engraving process so that the up-and down movement means may move the whole engraving head 50 upward. Then, engraving stylus 60 is moved in the X and Y directions to a predetermined position. Thereafter, the engraving head 50 is once again lowered to engraving surface T'. This repetitive process is time consuming.